<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!--内部样式-->
    <style>
        p{
            color: red;
            font-size: 20px;
        }
    </style>

    <!--外部样式-->
    <link rel="stylesheet" href="./css/hello.css">
</head>
<body>
    <p>welcome</p>
    <!--行内样式-->
    <div style="color: blue; font-weight: bold;">to</div>
    <h3>css</h3>
    <p>hello</p>
</body>
</html>